I was walking to class this morning and I came up with a few questions in regard to elemental oxygen and its limits.

1) How long can a human breathe pure O2 without harmful side-effects?
2) Where is elemental oxygen concentration the greatest on the planet, mountains, coastal, etc.?
3) Could we survive breathing pure elemental oxygen, and if so, for how long?

"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams